There is a sensor as one application example of a device manufactured by using a micromachining technique of a semiconductor called MEMS (Micro Electro Mechanical Systems). In a MEMS type sensor, it is important to consider a manufacturing variation and a manufacturing cost and to achieve a high accuracy and highly stable detection of very small physical quantities.
A background technique of the present technical field is disclosed, for example in PTL 1. In PTL 1, in an acceleration sensor which uses a principle of detecting acceleration from a displacement of a MEMS resonator, in order to prevent a vibration around a resonant frequency of a vibration system, a technique which suppresses the vibration by sealing the resonator at an atmospheric pressure and damping the resonator.
Further, the background technique of the present technical field is disclosed in PTL 2. In PTL 2, an electric oscillation circuit is provided with a detecting element having a structure in which a capacitance is changed in accordance with application of acceleration, and an impedance converter circuit in which a combined impedance and an inductor are equivalent, and a technique which detects acceleration indirectly from a control amount which controls a constant of a circuit element to keep a resonant frequency of the electric oscillation circuit constant is disclosed. According to this, since a resonance circuit can be obtained without manufacturing an inductor which is difficult to integrate, the oscillation circuit can be easily integrated. With this, a detecting circuit which detects a capacitance change due to application of acceleration can be formed in a small size, and higher sensitivity due to a high quality coefficient (Q value) of the oscillation circuit can be obtained.
Further, the background technique of the present technical field is disclosed in PTL 3. In PTL 3, a technique in which a spring softening effect in a detecting element having a structure in which a capacitance is changed in accordance with application of acceleration is used for a threshold of operation of an airbag is disclosed.